66 APPLIANCES FOR 



Number of animals Useful effort exerted by each 



per team. animal (ratio). 



1 ... ... ... 1-00 



2 ... ... ... 0-93 



3 ... ... ... 0-85 



4 ... ... ... 0-77 



5 ' ... ... ... 0-70 



6 ... ... ... 0-63 



7 ... ... ... 056 



8 ... ... ... 0-49 



Animals furnish per second mechanical work T given by 

 the formula : 



T=FV. 



But we cannot compel them to give us equivalent mechanical 

 work* as, for instance, to furnish us with an effort three 

 times greater with three times less speed. In other words, 

 we cannot apply the following formula: 



Y V 



3 10 



which is possible with other motors. For one must observe 

 a relation between the frequence of the movements of the 

 skeleton and those of the movements of the heart ; thus, a 

 man having sixteen respiratory movements per minute, can 

 only work a handle at the rate of 16, 32, 48, 56 revolutions 

 per. minute, or strike 8, 16, 24, 32 blows with a hammer. 

 Experience shows that when this concordance is not observed, 

 breathlessness occurs, the animated motor becomes fatigued 

 and quickly succumbs. 



In the application we are considering now, the resistance 

 of the implement is diminished by means of an intermediate 

 mechanism, in order to work the animal at its most favor- 

 able speed. This mechanism will absorb a part of the effort 

 for its own work. 



If k is the yield of the mechanism, 

 F the effort of the animal, 

 V its mean speed, 

 n a fixed co-efficient, greater than unity, we may write : 



V 



FV k = n F . 



* See Traits dt mtcanique experimentale, p. 141 ; Librairie Agricole. 



